1. Field of the Invention
The present invention relates generally to a broadcasting system, and in particular, to an apparatus and method for transmitting and receiving a frame including control information.
2. Description of the Related Art
Today, with the development of communication and broadcasting technologies, attempts are being made to find new ways to provide broadcast services in broadcasting systems or mobile communication systems, and discussions are currently underway on an advanced service capable of transmitting the common broadcast service such as voice and images, and also newer services such as packet data over broadcast service channels.
In addition, the broadcast services are making progress by adopting a variety of communication techniques to meet demands by users and consumers for digitalization, multi-channelization, broadband, high-quality, etc. Particularly, the increasing popularization of portable broadcast devices, including high-definition digital television and Portable Multimedia Player (PMP), has recently increased demands for various techniques to support the broadcast services.
FIG. 1 illustrates a frame structure for a broadcast service, to which the present invention is applied.
Referring to FIG. 1, a frame 101 includes a preamble 102, a Layer 1 (L1) signaling 103, a Layer 2 (L2) signaling 104, and at least one Physical Layer Pipe (PLP) 105, 106, . . . , 107. The preamble 102 includes information used to acquire time and frequency synchronization between a transmitter and a receiver, or to acquire synchronization for a frame boundary. The L1 signaling 103, which is a physical layer signaling, includes L1 static information 108, L1 configurable information 109, and L1 dynamic information 110. For reference, the L1 signaling is transmitted on a P2 symbol.
The L1 static information 108 includes information that is basically static over the passage of time. For example, the L1 static information 108 can include information on a cell identifier, a network identifier, a Radio Frequency (RF) channel number, a frame length, a pilot subcarrier location, etc.
The L1 configurable information 109 includes information that may change once in a while, although without changing on a frame-by-frame basis, i.e., information that generally lasts for a plurality of frames. For example, the L1 configurable information 109 can include information on a service identifier, a modulation order used for data transmission for an individual service, a code rate, etc. Herein, the unit in which the L1 static information 108 and the L1 configurable information 109 change is defined as a superframe, which includes at least one frame.
The L1 dynamic information 110 includes information that may change on a frame-by-frame basis. For example, the L1 dynamic information 110 can include information related to a location where each PLP is transmitted in the current frame. More specifically, the L1 dynamic information 110 can include information about a start point and an end point of a corresponding PLP, i.e., location information for a plurality of PLPs that are transmitted over the frame. These locations of the PLPs are subject to change in a next frame.
The L2 signaling 104 represents a Medium Access Control (MAC) signaling, and a PLP in which the L2 signaling is transmitted is also referred to as “PLP0”. The L2 signaling includes connection information between each PLP and a broadcast service channel. That is, the L2 signaling includes information indicating through which PLP a particular broadcast service is received.
A PLP_1 105, a PLP_2 106, and a PLP_N 107 transmit one or a plurality of broadcast service channels. The actual broadcast service data is transmitted through the PLP_1 105, the PLP_2 106, and the PLP_N 107. Therefore, the PLP_1 105, the PLP_2 106, and the PLP_N 107 can also be referred to as “data PLPs”.
Below, a process of receiving broadcast service channels will be described with reference to FIG. 1.
Referring to FIG. 1, a receiver acquires synchronization with the frame 101 through the preamble 102, and acquires information, such as a data transmission scheme or a frame length, from the L1 signaling 103. Thereafter, based on the L2 signaling 104, the receiver determines which PLP transmits the broadcast service channel it desires to receive. Thereafter, the receiver receives actual broadcast data through data PLPs corresponding to the PLP_1 105, the PLP_2 106, and the PLP_N 107. As described above, in order to receive a broadcast service channel, the receiver receives, in sequence, the preamble 102, the L1 signaling 103, the L2 signaling 104, and the data PLPs 105 to 107 for every frame.
In communication systems, in-band signaling has been proposed to prevent the receiver from receiving the preamble 102, the L1 signaling 103, the L2 signaling 104, and the data PLPs 105 to 107 in sequence every frame, when it receives a broadcast service channel for a predetermined long time. The in-band signaling scheme transmits dynamic information 110 of an L1 signaling in the next frame using a particular PLP.
FIG. 2 illustrates a frame structure that supports a broadcast service with a conventional in-band signaling scheme. More specifically, FIG. 2 illustrates frames that are consecutive in time.
Referring to FIG. 2, a frame #k 202 is followed by a frame #(k+1) 202. More specifically, the frame #k 201 and the frame #(k+1) 202 are transmitted consecutively in time for reception of a broadcast service channel. The frame #k 201 and the frame #(k+1) 202 include preambles 203 and 209, L1 signalings 204 and 210, L2 signalings 205 and 211, and data PLPs 206, 207, 212, 213, and 214, respectively.
Assuming that a receiver is receiving a particular broadcast service channel, and in the frame #k 201, the receiver receives the broadcast service channel through a PLP_2 207, when the in-band signaling scheme is applied, the PLP_2 207 includes dynamic information indicating a location of a PLP_2 in the frame #(k+1) 202 which is the next frame. That is, from in-band signaling information 216 included in the PLP_2 207 received in the frame #k 201, the receiver can acquire information 217 used to receive the PLP_2 213 in the frame #(k+1) 202, which is the next frame for receiving the same broadcast service channel. Accordingly, the receiver can check or identify a location of the PLP_2 213 that transmits broadcast data, depending on the in-band signaling in the PLP_2 207 of the current frame, without receiving an L1 signaling 210 through a P2 in the next frame #(k+1) 202.
More specifically, according to the in-band signaling scheme, the receiver, which has completed receiving up to the PLP_2 207 in the frame #k 201, can power off its devices for receiving a variety of information, e.g., the preamble 209, the L1 signaling 210, and the L2 signaling 211, until it receives the PLP_2 213 of the next frame #(k+1) 202. As can be seen, the in-band signaling scheme was intended to reduce the power consumption of the receiver.
However, with regard to support for the actual broadcast service, the receiver using the in-band signaling scheme may actually fail to directly or substantially gain the desired power reduction effect. Commonly, this is caused because, in the conventional in-band signaling scheme, a transmitter transmits only the dynamic information in the L1 signaling 210 through the P2 of the next frame #(k+1) following the current frame #k. For these reasons, the actual receiver must perform an operation of receiving the L1 signaling 210 through the P2 in the frame #(k+1) 202 because the receiver may not normally receive the broadcast service as it has no information on a change/no-change in other information except for the dynamic information in the L1 signaling 210, i.e., L1 static information and L1 configurable information.
Consequently, the receiver powers on its receiving units in order to receive other information, i.e., the L1 static information and the L1 configurable information, except for the dynamic information in the L1 signaling 210. As a result, the conventional in-band signaling scheme fails to result in the intended power savings for the receiver.
In addition, as the conventional in-band signaling scheme transmits only the dynamic information of the P2-L1 signaling 210 in the next frame for a period of a particular PLP, it may eventually fail to provide information on the change/no-change in information of the L2 signaling 211, which indicates a mapping relationship between each PLP and the broadcast service channel.
More specifically, even though information in the L2 signaling 211 transmitted through the PLP0 has changed, if the receiver fails to detect the change, a fatal error may occur when the receiver receives broadcast data later on. Therefore, even though the conventional receiver utilizes the in-band signaling scheme, it may still have to receive the preamble 209, the L1 signaling 210, the L2 signaling 211, and the data PLPs 212 to 214 in sequence.
Accordingly, the current broadcasting system needs a new in-band signaling scheme that addresses the problems caused by the application of the conventional in-band signaling scheme. In addition, there is a need for a more accurate broadcast service transmission and reception method that may still utilize the in-band signaling scheme but prevents at least some of the reception errors of the broadcast data.